I'm trying to date an Ottoman silver belt my wife inherited. The tughra, to me, looks like it could be from Mehmed V (27 Apr 1909-3 Jul 1918), but I'm not sure. Also, it looks like there is a 90 in Arabic at the 3 o'clock position. Am I seeing that right? The keyhole escutcheons are marked with what this site refers to as a Standard Mark. I don't know what the standards were or what this mark is telling me. I'd appreciate any help from the experts here. Thanks!